In the semiconductor industry, devices are fabricated by a number of manufacturing processes producing structures of an ever-decreasing size. Some manufacturing processes such as plasma etch and plasma clean processes expose a substrate to a high-speed stream of plasma to etch or clean the substrate. The plasma may be highly corrosive, and may corrode processing chambers and other surfaces that are exposed to the plasma.
Lids and nozzles are two important etch chamber components in conductor and dielectric etch. Typically lids and nozzles are made out of bulk ceramics. However, with a continuous decrease in device node, stringent defect requirements are dictated. Some of these newer applications use high operating temperatures (e.g., around 300° C. or above). Many bulk ceramics may crack due to thermal shock when used in such high temperature applications. Also, plasma resistant bulk ceramics are typically quite expensive.
Al2O3 may be used for lids and nozzles due to high thermal conductivity and flexural strength of Al2O3. However, under Fluorine chemistry, exposed Al2O3 forms AlF particles as well as Al metal contamination on processed wafers. Recent efforts have been made to coat the plasma facing side of the lid and nozzle with a thick protective coating. Thick-film coatings such as a plasma spray coating have been explored to reduce on-wafer metal contamination. However, vacuum sealing of the plasma spray coating has been a concern because in some instances the plasma spray coating does not maintain a vacuum due to inherent pores and cracks. Additionally, the plasma spray coating has a long lead time and typically is preceded by special surface preparation, which ultimately increases the cost. Also, refurbishing the coating can be a challenge due to surface preparation and cost.
The thin-film coating technique known as physical vapor deposition (PVD) has been considered for coating lids and nozzles. However, the PVD coating process is very slow (affects the ultimate cost of coating) and therefore may not generate coatings that are thick enough to meet the lifetime requirement of a component (especially for a non-consumable part like lid & nozzle). Additionally, PVD coatings typically have high residual stress, which in some instances will reduce the component lifetime due to coating cracking and peeling.